While there have been various studies on international law in domestic courts, the case of the Hong Kong Special Administrative Region of the People’s Republic of China [HKSAR], which celebrated its twentieth anniversary in 2017, presents unique questions. Under the principle of “One Country, Two Systems”, while the HKSAR maintains a distinct common-law system and a separate judicial regime, foreign affairs remain the responsibilities of the Central People’s Government of China. The handling of international law issues in cases before HKSAR courts would require consideration of the constitutional relation between the national (central) authorities of China and the local authorities in the HKSAR, and between the main legal system of China and the local HKSAR common-law system, in the light of the experiences of handling relevant cases in the past twenty years.